Polyetheramidoamine superabsorbent hydrogels

ABSTRACT

PCT No. PCT/EP93/00919 Sec. 371 Date Nov. 22, 1994 Sec. 102(e) Date Nov. 22, 1994 PCT Filed Apr. 16, 1993 PCT Pub. No. WO93/21256 PCT Pub. Date Oct. 28, 1993Polyetheramidoamine hydrogels consisting of polyetheramidomaine and/or polyamidoamine prepolymers crosslinked by Michael&#39;s nuceophilic polyaddition with alpha-omega-diamino monomers or with alpha-omega-diamino monomers or oligomers; said hydrogels having a swelling degree in water higher than 500% and are useful as superabsorbent materials.

The present invention relates to polyetheramidoamine hydrogels, toprocesses for the preparation thereof and to the use thereof assuperabsorbent materials.

The commonly so called superabsorbent materials are hydrophilicpolymers, having different chemical structure, which are capable ofabsorbing and retaining aqueous fluids even under moderate pressure inamounts equals to many time their own weight, without substantiallydissolving into the liquid itself.

Superabsorption characteristics are given by the presence, in thefundamental structure, of ionizable groups, which are generally of theanionic type (carboxylates) and are partially or totally salified; whenin contact with water, said groups dissociate and solvatate.

When dissociated, the functional groups along the polymeric chain havethe same electric charge, therefore repel each other.

This fact causes a widening of the polymeric lattice, therefore afurther absorption of water molecules is possible.

Generally, in order to avoid that such a process may lead to thedissolution of the polymer, this last is crosslinked by means ofsuitable agents as to make the gel substantially insoluble.

Accordingly, the absorption of water allows a substantial swelling ofthe polymer only.

Liquid absorption from polyelectrolytic superabsorbents is stronglyadversed by the concentration of dissolved electrolytic salts.

In fact, the ions, coming from the dissociation of the salts, interactwith the global charge of the macroion of the polymer, thus reducing therepelling potential between its functional groups, consequently also theabsorbing capacity will decrease.

As a consequence, the absorbing capacity drastically decreases passingfrom deionized water to saline aqueous solutions.

To date all the commercially available superabsorbent materials, such asfor example polyacrylates, CMC, etc, show such a sensitivity to salineconcentration (K. Nukushina; Chem. Abs. 94:66783 e).

Moreover, the gels of said superabsorbent polymers show the highestabsorbing capacity when the pH of the aqueous solutions, which they arecontacted with, is between 8 and 10.

Said absorbing capacity is strongly reduced in the pH range lower than5, as it can be seen from Table A ("Absorbency" by Pronoy Chatterjee,1985, pag. 206).

                  TABLE A                                                         ______________________________________                                        Effect of pH on the absorbing capacity of sodium polyacrylate.                          Free swelling capacity                                              pH        (g H.sub.2 O/g)                                                     ______________________________________                                        12        85                                                                  7         90                                                                  5         60                                                                  3         <10                                                                 ______________________________________                                    

The superabsorbing materials presently known belong to two main classes:

a) natural polymer derivatives containing anionic functional groups,such as carboxymethylcellulose, acrylonitrile grafted starches, etc;

b) completely synthetic polymers, such as polyacrylates,polyvinylalcohols, polyacrylamides, polyethyleneoxides, etc., which areobtained according to several processes, such as for example reversephase polymerization, radiation-induced polymerization, etc..

Superabsorbent materials are applied in several industrial fields: theiruse has been proposed in agriculture as sowing adjuvant, in building, inalkaline batteries manufacturing, in filter media manufacturing.

However, their main use, in association with cellulose fibers, is in thefield of the hygienic and sanitary products, as highly absorbingmaterial, used in lady's napkins, diapers for infants and incontinentadults.

It has now been found that crosslinked polyetheramidoamine polymers,obtained from primary or secondary diamines and containing ether andbisacrylamido groups, can gelify when absorbing aqueous liquids inamounts which are many times their own weight, thus showingsuperabsorbency characteristics.

U.S. Pat. No. 3,865,723 discloses both linear and crosslinkedpolyamidoamine derivatives as heparin complexing agents useful in thebiomedical field.

Polymers consisting of structures derived from primary amines ordi-secondary amines and bisacrylamides, both linear and crosslinked, bymeans of primary diamine, are described by Ferruti and Barbucci, Adv. inPolym. Sci. 58, p.55-92, Springer Verlag, 1984, wherein their use in thebiomedical field is provided.

In the hydrogels according to the invention the presence of polyetherchains advantageously enhances the hydrophilicity of the system. Infact, it seems that crosslinked polyamidoamine structures are not ableto absorb high amounts of water (Pesavento e al., J. Appl. Polym. Sci.,28, 3361-68 (1983)).

Polyetheramidoamines of the invention are obtained according to aprocess comprising the nucleophilic polyaddition of diamine monomers tocompounds bearing activated double bonds (Michael's type addition).

The addition reaction of an amino group to a double bond, which isactivated by the presence of an adjacent carboxyl group, by means ofhydrogen transfer (Michael's type) is described in DE 250214 and U.S.Pat. No. 3,445,441 wherein a similar mechanism is used to obtainpolyelectrolytic flocculants.

Hydrogels of the invention are formed by polymeric polyetheramidoamineand/or polyamidoamine chains ending with acryl groups, hereinafter namedas "prepolymers" in their turn crosslinked with suitable crosslinkingagents.

The prepolymers are obtained by a Michael's type nucleophilicpolyaddition, starting from bisacrylamido bifunctional monomers named[AA], of formula (I), ##STR1## wherein: R₁ is hydrogen;

[D] is C₁ -C₁₂ straight or branched alkylene unsubstituted orsubstituted with one or more hydroxy groups, optionally interrupted byoxygen atoms, or [D], together with N' and N", forms a piperazine ring,in which case R₁ is absent;

which are reacted with alpha-omega-diamino bifunctional monomers, named[BB], of formula (II): ##STR2## wherein: R₂ is C₁ -C₁₀ straight orbranched alkyl, optionally substituted with one or more hydroxy groups;

[E] is C₁ -C₁₂ straight or branched alkylene unsubstituted orsubstituted with one or more hydroxy groups, optionally interrupted byoxygen atoms; or the monomers [AA] are reacted with monofunctionalmonomers, named [B], of formula (IIa):

    H.sub.2 N--[F]--H                                          (IIa)

wherein [F] has the same meanings as [E] and can also be interrupted bytertiary amino groups. Preferred alkylene groups [D] are included in thefollowing formula (III): ##STR3## wherein a, b, c, d, e and f arenumbers 0 to 12, R₃ is methyl, hydroxy, C₁ -C₁₂ alkyl, optionallysubstituted with one or more hydroxy groups;

R₄ -R₉ are independently hydrogen or methyl.

Particularly preferred alkylene groups [D] are those which, togetherwith the nitrogen atoms N' and N", form the polyoxyalkylenediaminesknown under the commercial name Jeffamine®, manufactured by TexacoChemical Company.

Even more preferred monomers are monomers [AA], in which [D] is a groupof formula (III) wherein R₃ is methyl, R₄ is hydrogen, R₅ is methyl, aand b are 1, c is an integer 2 to 12 included, d, e, f are 0; or:

R₃, R₄ and R₉ are methyl, R₅ -R₈ are hydrogen, a and b are 1, c is about8.5, d is 0, the sum e+f is about 2.4;

or:

a, d, f are 0, b is 2, c and e are 1, R₄ -R₇ are hydrogen. Particularlypreferred are bisacryloylpiperazine (BAP), methylene-bis-acrylamide(BAC), dihydroxyethylenebisacrylamide (DHEBA).

Particularly preferred compounds of formula (II) are those in which R₂are both 2-hydroxypropyl, [E] has the following formula: ##STR4##

In some particular cases monofunctional monomers (IIa) are used as chainextending agents between two monomers [AA].

The resulting prepolymer has the following formulae:

    {[AA] [BB]}.sub.x

or

    {[AA] [B]}.sub.x {[AA] [BB]}.sub.y

wherein x and y are numbers 1 to 50.

The cross-linking of the resulting prepolymer takes place throughMichael's nucleophilic polyaddition.

For the cross-linking at least tetrafunctional crosslinking agents areused, of formula (IV):

    H.sub.2 N--[G]--NH.sub.2                                   (IV)

wherein:

[G] is C₂ -C₁₂ straight or branched alkylene, unsubstituted orsubstituted with one or more hydroxy groups, optionally interrupted byoxygen atoms and/or ##STR5## amino groups, wherein R₁₀ is hydrogen or C₁-C₄ alkyl.

Preferred compounds are those of formula (IV ), wherein [G] representsthe polyoxyalkylene residues known by the commercial name Jeffamine® ofthe M, D, ED, C-346, DU, EDR-148 and T series, described in thepublication by Texaco Chemical Company "The JEFFAMINE®Polyoxyalkyleneamines", 1987.

Among the crosslinking agents, Jeffamine DU-700(polyoxyalkylenediamines) is particularly preferred.

The stoichiometric ratio, considered in equivalents, of the monomer [AA]to the sum of the monomer [BB] with the crosslinking agent must be suchthat the number of acryl bonds on [AA] be the same as the number of thehydrogen atoms bound to the amino nitrogen atoms, i.e., each molecule[AA] corresponds to one molecule [BB] and to half a molecule of thecrosslinking agent.

Cross-linking can be carried out according to two different methods.

a) in two steps, first preparing the prepolymer {[AA] [BB]}_(x), which,optionally after recovering it, is reacted with the crosslinking agent;

b) in a single step, wherein the monomers and the crosslinking agent/sare reacted simultaneously.

The reaction medium consists of a polar solvent or a mixture of polarsolvents, such as water or water-miscible alcohols. The reactiontemperature ranges from 0° to 60° C., preferably from 20° to 40° C.

The hydrogel will have different cross-linking degrees, depending on thedesired physical characteristics.

The final product will be elastic and have a swelling degree in water atleast higher than 500%.

The hydrogels of the present invention show the important advantage toabsorb liquids in a way which is practically independent from salineconcentration, contrarily to the presently known superabsorbentproducts, whose absorption capacity is strongly affected by the presenceof electrloytes.

The following examples further illustrate the invention.

EXAMPLE 1

JAEJ 10%

7.6 g of BAP (39.18 mmoles), under stirring, in nitrogen atmosphere wereadded to 6.78 g of JC346 (19.59 mmoles) in 17 ml H₂ O. The solution wasthen allowed to react for 2 days at room temperature, without stirring,shielding from the light. Then 0.9 g of Jeffamine D230(polyoxyalkylenediamines) (3.91 mmoles) and 0.94 g of EDA(ethylenediamine, 15.64 mmoles), previously dissolved in 4 ml of 1:3MeOH/H₂ O mixture were added. Crosslinking reaction was carried out for3 days at room temperature. After several washings with MeOH (methanol)and drying under vacuum at room temperature a yellow, friable gel wasobtained. (62% yield).

EXAMPLE 2

JAJ 25%

6.78 g of BAP (34.9 mmoles), under stirring, in nitrogen atmosphere wereadded to 6.04 g of JC346 (17.45 mmoles) in 16 ml H₂ O. The solution wasthen allowed to react for 4 days at room temperature, without stirring,shielding from the light. Then 2.0 g of Jeffamine D230(polyoxyalkylenediamines) (8.72 mmoles) and 1 ml of MeOH were added.Cross-linking reaction was carried out for 3 days at room temperature.After several washings with MeOH and drying under vacuum at roomtemperature a yellow, soft gel was obtained. (50% yield).

EXAMPLE 3

JAEJ 5%

5.97 g of BAP (30.74 mmoles), under stirring, in nitrogen atmospherewere added to 5.32 g of JC346 (15.37 mmoles) in 15 ml H₂ O. The solutionwas then allowed to react for 4 days at room temperature, withoutstirring, shielding from the light. Then 0.35 g of Jeffamine D230(polyoxyalkylenediamines) (1.37 mmoles) and 0.37 g of EDA(ethylenediamine, 6.15 mmoles), and 1 ml of MeOH were added.Crosslinking reaction was carried out for 3 days at room temperature.After several washings with MeOH and drying under vacuum at roomtemperature a 90% yield was obtained.

EXAMPLE 4

JA'Jed9 bis (FA 62)

3.17 g of BAP (20.62 mmoles) and 4.64 g of Jeffamine ED900(polyoxyalkylenediamines) (5.15 mmoles) were added to 3.57 g of JC346(10.31 mmoles) in 22.8 ml H₂ O. Cross-linking reaction was carried outfor 3 weeks at room temperature. After several washings with MeOH anddrying under vacuum at room temperature 80% yield was obtained.

EXAMPLE 5

DAEJ 5%

5.81 g of BAC (29.9 mmoles) in 15 ml H₂ O were added to 2.16 g of DMESA(14.9. mmoles). The solution was then allowed to react for 3 daysshielding from the light. Then 0.34 g of Jeffamine D230(polyoxyalkylenediamines) (1.49 mmoles) and 0.35 g of EDA (5.98 mmoles)and 4 ml of MeOH were added. After 1 day a gel was obtained which waswashed with MeOH after four days and dried under vacuum at roomtemperature after 4 days, giving a yellowish, brittle gel (88% yield).

EXAMPLE 6

DA'EJ 5%

4.8 g of BAC (31.2 mmoles), in 15 ml H₂ O were added to 2.25 g of DMESA(15.6 mmoles). The solution was then allowed to react for 3 days,shielding from the light. Then 0.36 g of Jeffamine D230(polyoxyalkylenediamines) (1.55 mmoles) and 0.36 g of EDA (6.23 mmoles)and 1 ml of MeOH were added. After 1 day a gel was obtained, which waswashed with MeOH and dried under vacuum at room temperature after 4days, giving a transparent, brittle gel (85% yield).

EXAMPLE 7

DA'ed9 /edr (FA 55)

1.14 g of BAC (7.44 mmoles) and 55 mg of Jeffamine EDR 148(polyoxyalkylenediamines) (3.72 mmoles) in 14 ml H₂ O were added to 3.01g of Jeffamine ED900 (3.34 mmoles). After 10 days, the product wasrepeatedly washed with MeOH and dried under vacuum at room temperature.

EXAMPLE 8

JAed9/edr (FA 56)

0.47 g of BAC (2.46 mmoles) and 18 mg of Jeffamine EDR 148(polyoxyalkylenediamines) (0.12 mmoles) in 6 ml H₂ O were added to 1.0 gof Jeffamine ED900 (polyoxyalkylenediamines) (1.11 mmoles). After 10days, the product was repeatedly washed with MeOH and dried under vacuumat room temperature.

EXAMPLE 9

JA'ed9/Das (FA 57)

1.118 g of BAC (7.26 mmoles) and 33.7 g of Jeffamine EDR 148(polyoxyalkylenediamines) (0.383 mmoles) in 14 ml H₂ O were added to3.10 g of Jeffamine ED900 (polyoxyalkylenediamines) (3.44 mmoles). After15 days, the product was repeatedly washed with MeOH and then withhexane and dried under vacuum at room temperature.

The obtained hydrogels were subjected to swelling tests both indistilled water, and in saline solution (1% NaCl).

The results are shown in the following Tables:

                  TABLE 1                                                         ______________________________________                                        Products obtained with Jeffamine C346 (polyoxyalkylenediamines)               and BAP in 1:2 ratio and subsequent cross-linking with the                    compounds shown in the Table:                                                          Crosslinking agent                                                            (referred to JC346                                                                         Swelling                                                Gel        taken as 1 in          in NaCl                                     (code)     moles)         in H.sub.2 O                                                                          1%                                          ______________________________________                                        JAEJ 10%   JD230 (0.2)    750     850                                                    +EDA (0.8)                                                         JAJ 25%    JD 200 (0.5)   690     610                                         JAEJ 5%    JD230 (0.1)    600     690                                                    +EDA (0.4)                                                         JAed6-25%  JED 600 (0.5)  970     1130                                        JAed9-25%  JED 900 (0.5)  780     730                                         JAed9 bis  JED 900 (0.5)  1650    1340                                        (FA 51)                                                                       (25% H.sub.2 O)                                                               ______________________________________                                         Note:                                                                         The reaction between Jeffamine C346 (polyoxyalkylenediamines) and BAP         occurs in 60% w/w aqueous solution for 2 days at room temperature.            The crosslinking then occurs by addition of the crosslinking agent/s,         according to a Michael's type addition mechanism.                        

                  TABLE 2                                                         ______________________________________                                        Products obtained with Jeffamine C346 (polyoxyalkylenediamines)               and BAP in 1:1,1 ratio, crosslinking with ethylenediamine (EDA)                      Crosslinking agent                                                            (referred to JC346                                                                          Swelling                                                 Gel      taken as 1 in           in NaCl                                      (code)   moles)          in H.sub.2 O                                                                          1%                                           ______________________________________                                        JBE 5%   EDA 0.05        1860    1320                                         JBE bis  EDA 0.05        2220    2380                                         (FA 52)                                                                       ______________________________________                                         Note:                                                                         For the product JBE 5% the addition of the crosslinking agent occurs in       subsequent times. The product FA 52 (JBE 5% bis) has been obtained by         contemporaneously mixing reagents and crosslinking agents.               

                  TABLE 3                                                         ______________________________________                                        Products obtained with Jeffaimine C346 (polyoxyalkylened-                     iamines) and BAC in 1:2 ratio and subsequent cross-linking with               the compounds shown in the Table:                                                      Crosslinking agent                                                            (referred to JC346                                                                         Swelling                                                Gel        taken in 1 in          in NaCl                                     (code)     moles)         in H.sub.2 O                                                                          1%                                          ______________________________________                                        JA'EJ 10%  JD230 (0.2)    1860    1320                                                   +EDA (0.8)                                                         JA'EJ 5%   JD230 (0.1)    605     690                                                    +EDA (0.4)                                                         JAed6 bis  JED 600 (0.5)  480     680                                         (FA 47)                                                                       (H.sub.2 O)                                                                   JAed9 bis  JED 900 (0.5)  690     830                                         (FA 62)                                                                       (H.sub.2 O)                                                                   ______________________________________                                         Note:                                                                         The products FA 47 (JA'Jed6 bis) and e FA'Jed9 bis were obtained by           contemporaneously mixing reagents and crosslinking agents.               

We claim:
 1. Polyetheramidoamine hydrogels consisting ofpolyetheramidoamine and/or polyamidoamine, prepolymers containing anactivated double bond which is susceptible to the Michael's nucleophilicpolyaddition, crosslinked with alpha-omega-diamino monomers oroligomers, with the proviso that at least one of the prepolymer or ofthe alpha-omega-diamino monomers or oligomers contains a polyetheralkylene chain.
 2. Hydrogels according to claim 1, wherein theprepolymers have the formulae:

    {[AA] [BB]}.sub.x

or

    {[AA] [B]}.sub.x {[AA] [BB]}.sub.y

wherein x and y are numbers 1 to 50, wherein: [AA] is a compound offormula (I): ##STR6## wherein: R₁ is hydrogen: is C₁ -C₁₂ straight orbranched alkylene unsubstituted or substituted with one or more hydroxygroups, optionally interrupted by oxygen atoms, or together with N' andN", forms a piperazine ring, in which case R₁ is absent; [BB] is acompound of formula (II): ##STR7## wherein: R₂ is C₁ -C₁₀ straight orbranched alkyl, optionally substituted with one or more hydroxy groups;[E] is C₁ -C₁₂ straight or branched alkylene unsubstituted orsubstituted with one or more hydroxy groups, optionally interrupted byoxygen atoms; [B] is a compound of formula (IIa):

    H.sub.2 N--[F]--H                                          (IIa)

wherein [F] has the same meanings as [E] and it can also be interruptedby tertiary amino groups.
 3. Hydrogels according to claim 2, wherein [D]is a group of formula (III): ##STR8## wherein a, b, c, d, e and f arenumbers 0 to 12, R₃ is methyl, hydroxy, C₁ -C₁₂ alkyl, optionallysubstituted with one or more hydroxy groups;R₄ -R₉ are independentlyhydrogen or methyl.
 4. Hydrogels according to claim 2, whereinbisacrylamides [AA] are selected from the group consisting ofbisacryloylpiperazine, methylene-bis-acrylamide,dihydroxyethylenebisacrylamide, bisacrylamides wherein the group [D],together with the nitrogen atoms N' and N", formpolyoxyalkylenediamines.
 5. Hydrogels according to claim 2, whereincompound [BB] of the formula: ##STR9##
 6. Hydrogels according to claim 1wherein the prepolymers are crosslinked with compounds of formula (IV):

    H.sub.2 N--[G]--NH.sub.2                                   (IV)

wherein: [G] is C₂ -C₁₂ straight or branched alkylene, unsubstituted orsubstituted with one or more hydroxy groups, optionally interrupted byoxygen atoms and/or NR₁₀ amino groups, wherein R₁₀ is hydrogen or C₁ -C₄alkyl.
 7. Hydrogels according to claim 1 wherein the prepolymers arecross-linked with compounds of the formula H₂ N--[G]--NH₂ wherein [G]represents polyoxyalkylene residues.
 8. A process for the preparation ofthe hydrogels of claim 2 which comprises crosslinking the prepolymers ofsaid formula {[AA] [BB]}_(x) or {[AA] [B]}_(x) {[AA] [BB]}_(y) withcrosslinking agents of formula (IV)

    H.sub.2 N--[G]--NH.sub.2                                   (IV)

wherein [G] is C₂ -C₁₂ straight or branched alkylene, unsubstituted orsubstituted with one or more hydroxy groups, optionally interrupted byoxygen atoms and/or NR₁₀ amino groups, wherein R₁₀ is hydrogen or C₁ -C₄alkyl through a nucleophilic polyaddition mechanism, in a polar solvent,at a temperature from 20° to 40° C., shielded from light.
 9. Asuperabsorbing material having as the absorbing ingredient the hydrogelsof claim 1.